Earth boring equipment for core recovery



June 22, 1965 r. E. RASSIEUR 3,190,377

EARTH BORING EQUIPMENT FOR CORE RECOVERY Filed March 30, 1960 3 Sheets-Sheet 1 r I I "/I I I I I I I I I I I I I l I I I l I I I I I I 42 I I I I I I I I I I I I I I I I I I I I I I I/ June 22, 1965 'r. E. RASSIEUR 3,190,377

EARTH BORING EQUIPMENT FOR CORE RECOVERY Filed March so, 1960 s Sheets-Sheet 2 FIGS Q I 5W, WWW

June 22, 1965 r. E. RASSIEUR EARTH BORING EQUIPMENT FOR CORE RECOVERY Filed March 30, 1960 3 Sheets-Sheet 3 m r 6 8.. W W NM M \w a m 7 9m w 0 mm. W 5 \\\\\\\\\\\R- M H I m I I M M fl @F v 0 m M I U \\\\\Nm r %Q m\ V m 7 B Q 50E m9. Q 8* N3 QM- I Y I I I l l I I I I H I II lll I III. TI Mm I QQ \I Iv/ -12 mm NM wm QY Q \\-Y\ United States Patent 3,190,377 EARTH EGRENG EQUIPMENT FQR CURE RECGVERY Theodore E. Rassieur, University City, Mo, assiguor to (Ientral Mine Equipment Company, St. Louis, Mo a corporation of Missouri Filed Mar. 3t 19%, Ser. No. 125,570 3 @iainrs. (Cl. 175-257) This'invention relates to core recovery earth boring equipment and more specifically to an arrangement of, and'interconnection of, sectional stems and adapters to facilitate alternative procedures for hole drilling and for core recovery from the hole.

The earth boring equipment, to which this invention relates, is adapted to drive rotary bits or cutters to varying depths, sometimes as much as 300 or 400 feet. It will be appreciated that the drill string for driving these bits or cutters must be sectional with detachable couplings arranged between the sections, so as to make handling convenient. At intervals during the boring of test holes, it is necessary to obtain sample cores to determine the geological information necessary from the test hole. With many types of equipment not specially designed for this purpose, it has been necessary to remove the bit from the hole by disassembling the drill string driving the bit section by section. Once the bit has been removed a coring bit is substituted, and the string reassembled section by section, so as to cut the core from the bottom of the hole. When the core is cut, the core is removed by the same process, that is, each time a change of bits was necessary the drill string sections had to be disassembled and then reassembled, which is obviously a slow and ineflicient process. Furthermore, in the cutting of the core, it was inevitable that some of the material from the wall of the hole would be trapped in the coring tool. Accordingly, the core cut was not a true sample from the bottom of the hole, exclusively. To avoid the heavy work of assernbiing and disassembling the heavy drill stem sections necessary to drive the heavy cutting hit each time a coring operation is necessary, it is proposed that the cutting bit he made hollow, and that the drill string be composed of tubular sections with unobstructed internal passage, so that the coring tool on the end of its own sectional string of lighter sections may be inserted through the tubular sections of the main drill string and the hollow bit, so as to obtain the core without removing the heavy sections of the drill string necessary for driving the main cutting bit.

boring equipment which is rugged and durable, and yet easily and readily coupled or uncoupled.

. It is another object of this invention to provide earth boring equipment which may be driven by a tubular drill string with an unobstructed inner surface.

It is another object of this invention to provide earth boring equipment which is tubular with suitable couplings which are compact, rugged and easily connected.

it is another object of this invention to provide earth boring equipment with couplings between detachable sections for transmitting rotary motion which couplings are reinforced by arrangement of an external conveyor flight, but which do not interfere with the function of the conveyor flight.

According to this invention, a hollow main boring bit is detachably connected with a tubular sectional drill stem to which an external conveyor flight is secured. The detachable connections between the bit and between the sections of the stem are each external, so as to leave an unobstructed central passage. A pilot bit is arranged to be movable through the tubular drill stem and the hollow main bit on its own sectional drill stem. When it is necessary to perform a coring operation, the pilot bit and its drill stern may be separately removed, and the pilot bit replaced with a coring tool and lowered through the main drill stem to perform the coring operation. During this procedure, the main drill stem acts as a well casing to prevent contamination of the core sample by loose material within and above the bottom of the hole.

The following detailed specification taken with the accompanying drawings will enable any person skilled in the art or science to which the invention pertains to make and use the same. In the drawings:

FIG. 1 is an environmental view in elevation showing the general arrangement of the parts;

FIG. 2 is a longitudinal sectional view of the adapter unit parts for connection with the drill stem and drill head chuck;

FIG. 3 is a plan view of the main drill stem illustrating one form of coupling;

H6. 4 is a plan view partly in section illustrating the main boring bit for connection with a drill string coupling part;

FIG. 5 is a longitudinal sectional view of the plug for connection with the pilot bit or a coring bit;

FIG. 6 is a longitudinal section taken on the center line of a main drill stem section;

FIG. 7 is an enlarged view of a coupling with the conveyer flight removed;

FIG. 8 is an enlarged view of a second form of coupling with the conveyer flight removed; and

FIG. 9 is a plan view partly in section of one section of auxiliary stem.

The general arrangement of parts in the construction, according to this invention, is shown in FIG. 1. A rotary rig which is usually portable furnishes the driving power for rotating the drill string to produce the boring action of the bits at the opposite end of the string. The rig forms no part of the instant invention, and merely for illustrative purposes the head H of the rig is shown. This has a driven chuck part CH adapted to be coupled with an adapter A, hereinafter described in detail. The adapter A, in turn, drives one or more sections of main drill stem MS, which are coupled together, and at their lower end connected with a hollow bit HB by suitable couplings, hereinafter described. Internally of the main drill stem are the coupled sections of auxiliary stem AS, which, in turn, has an internal socket coupling connection within the adapter A. The sections of the auxiliary stem are, in turn, connected with a plug PS, and the lower end of the plug is coupled with a pilot bit PB.

From this broad general description of the parts, it will be readily appreciated that the couplings between the adapter A and the main and auxiliary stems make it possible to drive both stems simultaneously from the head H or" the drill rig, and this is the normal boring procedure. The main drill stem operates the main hollow bit HB, while the auxiliary stem AS rotates the pilot bit PB. The pilot bit leads the main bit during the boring operation, so that the hole will be maintained straight. Both bits, however, operate to cut away a hole suliicient in size to allow the downward passage of the spiral flight SF on the main drill string, and as the boring progresses the cuttings are removed from the hole by the action of the spiral flight SF. As the bits penetrate into the hole, th head,

adapter raisedout of the way and additional drill; stern sections are added. ,The adapter A'is then lowered into coupled relation with the stems, and the'boring operation continues. e

The several parts of the drilling equipment arenow described in more detail, it being appreciated that the specific parts are described here only for purposes of illustration of a mechanism capable of carrying out these procedures. FIG. 4 shows one form of hollow bit' HB, which "is basically a structure having a heavy collar, such as 10, plug welded to a short section of drill stem, such as 11. The collar carries a pair of radially located socket members 13 and 14, which socket members have tapered internal passages each carrying a pair of cutters or bits15 and 16 in socket 14 and 17 and18 in-socket 13. The

sockets -13 and 14 are so arranged that the bits v15, 16 and 17 and 18 are angularly inclined with respectto the axis of the bit, so as to cut a hole which is larger than the circumference of the collar 10 with the sockets 13' rated circumferentially by sockets, such as .22, :one of' which is shown. Each jaw 20 and 21 embraces the tubular section 11 and is plug welded thereto at 24'and 25. The tubular section 11, in turn, is drilledradially at 26.

As heretofore stated, the hollow bit HB is rotated by a sectional drill stem MS, such as shown in FIG. 3, coupled one section to another and one section of which is shown in FIG. 6. Referring specifically to the sectional view in FIG. 6, the main drill stem is composed of apluralityof sections one of which is shown. Essentially each section MS is .a tubular body 30. Each end of the tubular body has a coupling collar, such as 31 at one end 'and'32 at the opposite end, collar 31 is welded or, otherwise suitably secured at 33 to the tubular body '30, and projects beyond the end of the tubular body 30 to form an internally stepped end for the section of the drill stem MS. Collar 31 has projecting jaws 35 and 36,,one of which is shown in FIG. 6. Between'the jaws are sockets 38 and 39. These sockets 38. and 39 may receive the jaws 20 and21 of the hollow main bit HR, for example, or may be coupled with another section of drill string MS. How- 7 ever, assuming that FIG. 6 shows the lowest section of the drill stem whichsupports the bit HB, then the'jaWs 35 and 36 (not'shown here) fit into the sockets 22 and 23, one'of which is shown in FIG. 4. Collar 31 of the coupling has a threaded socket. radially thereof shown at 40, and this socket 40 may threadedly receive a dog-point set screw, which has an end portion projecting into the hole 26 in the sleeve 11 of the hollow bit HB to prevent longitudinal or axial separation between the bit'HB and the section of the main drill stem MS shownin FIG. '6.

At the opposite end of the collar of the drill stem MS is the collar 32 through which the tubular body 30 pro jects, so as to form an externally stepped end at the opposite end of this section of the main drill stem MS. Collar 32 has jaws, such as 42 and 44, which will be hereiuafter described in detail. Between the jaws 42 and 44 are sockets 43 and 45, one of which is shown in FIG. 6. 'A spiral conveyer flight SF extends from a point at the end face of the collar 31 to a point at the end face of the collar 32. Because the spiral flight SF-is welded to each of the collars and to the tubular stems 30, the spiral'flight is' a welded reinforcement'for the stem and both the coupling collar 317and couplingcollar 32. Because of the particular arrangement of the'flight with respect to the collars 31 and 32, the spiral flight SF is a circumferentialreinthemselves, thus the arrangement of flight on the tubular stern -MS amounts to a reinforcement against strains imposed by torsion or bending of the stem 3% and its sleeves 31 and 32, which are the torsion transmitting parts of the stern section MS. This is a definite step forward in drill stem construction since the reinforcement will minimize whipping or the stem in the hole each time the main bit I-IB encounters increases and sudden decreases in torsion resistance, such asv are normally encountered by the bit HR during the boring operation. One way of explaining this reinforcing action is'to point out that twisting the stem 30 will cause a stress in the fiight SF tending to wind it up on the stem to compress the stemabout its periphery and also the couplings. The flight also reinis, of course, adapted by its externally stepped contour and the arrangement of jaws 42 and 44 on the sleeve 32 to engage and be coupled with a similarly formed drill stern-MS, suchas heretofore described m detail. It is also, of course, adapted for coupling with the adapter A shown in FIG. 2. This adapter isprimarily used as the driving connection between the main drill string MS and the head H of the drill rig. Asshown in FIG. 2, the adapter A has a square or hexagonal shank carrying a flanged-fitting, such as 51. A pair of concentric sleeve members, such as 53 and 54, are welded'at their upper ends within sockets 56 and 58 form-ed concentrically in the flange 51. Sleeve 54 is tubular, and of the same size and shape as the sleeve 31 on the drill stems MS. Jaws 59 and 60, one of which is shown, project axially of the sleeve 54, andare separated by sockets 62 and 64. A tapped hole 65 in thesleeve 54 is provided for a pin bolt, such as is heretofore described, for coupling with another section ofthe drill string sections MS.

This construction of the sleeve 54 adapts it to be telescoped over the tubular portion 30 of a section of a drill stem, such as MS, so that jaws 59 and 60 protrude into sockets 43 and 45, while sockets 62 and 64 receive jaws 42' and 44. The pin bolt can then be threaded into the aperture 65, so as to project into the hole 41" to attach the adapter to the main drill string MS. The internal bore of sleeve 53is preferably hexagonal to receive a coupling parton the auxiliary drill string AS, hereinafter described, andthe shank 50 is'apertured at 52'for a connecting pin which is inserted through the hole 52a in the chuck CH forcement'which will prevent any strain imposed on the jaws 35, 36, 42, 44 from swelling the sleeves or the jaws of the head. Both sleeves 53 and 54 have aligned apertures 71,72,73 and 74. This permits the insertion of a key or' a bolt through these apertures, so as to connect the sleeve 53 with' the coupling part on the auxiilary drill stem, ashereinafter described. a

" The sections of the auxiliary drill stem are more or less conventional inconstruction, and one section is illustrated in detail in FIG. 9. The auxiliary sections of the drill stem AS have a main tubular body, such as 80, with a square or hexagonal shank 81 atone end and a sleeve, such as 82 at the'opposite end having a hexagonal socket 83. The shank 81' is drilled to form an aperture 85 throughwhich a pin may be inserted to connect the auxiliary drill stem AS with another stem of like construction, or with the adapter A above described. The socket 82 has aligned apertures, such as 87 and 88,through which a pin,or the like, may be inserted to connect the socket 82 .with the'shank of another section of auxiliary drill stem or with a plug, such as illustrated in FIG. 5, it being understood thattheplug forms the direct connection between the auxiliary drill stem and the pilot bit PB. The plug is constructed slightly diilerent than the sections of the auxiliary drill stem just described and to which it is connected. The body of the plug is a tubular section 90, the upper end. of which receivesa bushing 91 welded therein at 92; Athexagonal shank- 94 is drilled at 95 to form an aperture for pin connection with one of the sockets 82 on one of the auxiliary drill stemsections.

Shank 94 has a flange 96 and a square or hexagonal extension, such as 98, which is received in a similar contoured aperture in the bushing 91. As shown, the shank 94 is welded into the aperture of the bushing 91. Tubular section 9@ of the body has peripheral grooves 9 and 1131'? I receiving O-rings of rubber, or the like, and the outside dimension of the tubular body t) is such that it has a sliding fit within the tubular section 3% of the main drill string sections MS, as well as with the internal periphery of the sleeve 11 of the main hollow bit E8, the rings received in the grooves 99 and ltiil form a tight seal against the leakage of fluid or dirt into the interior of the sleeve 11 of the hollow bit HB, so as to prevent the accumulation of corrosion, mud, or the like, from interfering with the free withdrawal of the auxiliary drill stem from within the main drill stem. At the lower end of the tubular body 9%) is a hollow bushing 1633, which is welded at Til-4 to the tubular body of the plug 9t). Bushing 103 has a square or hexagonal aperture to receive the sleeve 1%, which is in turn welded in the bushing 1133. Sleeve 105 has a hexagonal bore forming a socket to receive a hexagonal shank 1% of the pilot bit PB, shank 1%, in turn, is drilled to form an aperture 1W, which aligns with the apertures litlfi and it? in the socket 165. A pin key, or the like, connects the pilot bit with the plug PS by insertion through the apertures 167, 108 and 1%.

The construction, heretofore described, when assembled is adapted by its construction to form an earth boring operation in a satisfactory manner. It is also obvious from the manner of construction that the two drill stems,

the main drill stein MS and the auxiliary drill stem AS,

are connected to be rotated together by the adapter A, shown in FIG. 2, and as the boring progresses the head H follows the adapter downwardly, as the bits penetrate.

. The cuttings from the borings are removed from the hole by this continuous spiral flight, which extends from the face of the lowest sleeve 31 in the coupling of the main drill stem MS to a point above the ground surface from which the upper section of the main drill string MS projects. Each coupling is adapted for external operation by the pin bolt connection, and the pin bolt itself is located behind the inactive face of the spiral flight, so as to be protected from dirt and abrasion. The addition of sections, as the boring operation progresses, is facilitated by the simple removal of the pin bolt from the adapter A and the key bolt through the apertures 71 to '74, inclusive. lhis disconnects both the main drill string and the auxiliary string from the adapter, and the head may then be raised, and new sections connected with both the adapter and the drill strings. Furthermore, it is possible with this equipment to remove the auxiliary string and the pilot bit without removing the main drill string, by simply removing the pin bolt from the adapter hole 65 to disconnect the adapter and the main drill'string. After this disconnection is made, the raising of the head of the drill rig will remove the auxiliary string, and this can be done in a step by step manner, disassembling the auxiliary drill stem section by section, so that the pilot bit may be replaced by a coring tool, and the coring operation performed in the usual manner.

Turning now to FIG. 7, which shows an assembled coupling for the main drill string MS on an enlarged scale, it will be noted that the tubular stems 3i mount the collars $1 and 32. Collar 31 has a pair of jaws, one of which is shown at 36, which fit into a pair of sockets, one of which is shown at 45, in the sleeve 32. Likewise, sleeve 31 has a pair of sockets 3S and 39, which receive a pair of jaws 42 and 44, respectively, of the sleeve 32, both sleeves are securely welded to the exterior of the tube 3%, or tubes 3%), respectively, a dog-point screw 49a is threaded in the threaded opening an in the sleeve 31, and has a pin point, or pin end, projecting into the tube 3%. As will be evident from this enlarged section, the tubes 30 come into abutting relation within the sleeve 31, so as to form a continuous tubular wall through which the auxiliary stems may project without interference. The dog-point screw dtla extends only flush with the inner wall of the tubular stem 3%), and this is all that is necessary to form the rigid coupling connection between two sections of the drill stems MS. The dog-point set screw carries none of the bending or the auxiliary stresses. The pin bolt being subject only to sheer forces of a magnitude commensurate with the weight of the drill string and bit below the particular pin bolt when the drill string is removed from the hole.

Turning now to FIG. 8 which shows a modification of a coupling for the main string MS, it will be observed that the main string MS is again formed of tubular sections, in this case indicated as 139. Corresponding parts in this modification are indicated by similar reference characters with the prefix 1. Thus, connecting opposite ends of stem sections are shown as 139, it being understood that in this particular case FIG. 8 illustrates the lower end of the drill stem 130, and the upper end of a drill stem 1319. The lower end of each drill stern section i) has asleeve 131 with a tapped hole for receiving a dog-point set screw, the pin end of which projects into the hole 141 in the upper end of the drill string section 13%. As will be seen, the function of the dogpoint set screw is merely to resist separation of the sections. The strain due to torsion and compression, that is the weight of the sections in compression as borne by the bit, is taken up by direct contact between the ends of the drill string sections 139. The lower end of the drill string section 130 has jaws 142 and 144 received in slots 13-8 and 14.39, respectively, of the upper end of the next adjacent drill string 13%. The upper end of the lower drill string 130 has jaws 136 and a jaw 137, not shown in this view, which are received in these slots 145 and the slot 146, which does not appear in this view, but is diametrically opposite the slot 145. The sleeve 133i is capable also of being used with the hollow main bit Hi3 by telescoping the sleeve 131 over to 11, but the upper end requires a slightly diiierent adapter with a tubular section constructed in the same manner as the lower end of each of the drill string sections 139. Otherwise than this, the two types of couplings, herein'oefore described, are interchangeable, both having internally stepped ends and externally stepped ends which telescope to form a coupling.

Operation As heretofore explained, the equipment disclosed provides for earth boring operations, in which a core sample can be obtained without disassembly of the heavy main drill stern section. The coring operation is performed by simply removing the auxiliary stem sections and substituting a coring tool, and is accomplished without removal of the main drill sections, which can act as a well casing during the coring operation. These results can be obtained, as above pointed out, because of the novel type of couplings used in the main drill sections of the drill stem, which in turn are adapted to couple the stem, both at the driving end and at the bit end, to suitable tools, so that the operations of boring and of coring may be separately carried out without interference.

it is contemplated that other modifications will occur to those skilled in the art which come within the scope of the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. in an earth boring tool adapted for core recovery, including a hollow main bit, a sectional tubular drill string of pipe sections having the same external size and the same internal size connected end to end to form a smooth unobstructed inner surface and at one unconnected end to a hollow main bit, a pilot bit of a size to be movable into said hollow main bit through said tubular drill string and adapted to be independently manipulated by an auxiliary drill string extending through said main drill string and connected to said pilot bit, the

improvement in said earth boring tool of means for separately connecting said pipe sections end to end and to said hollow main bit comprising,-

(a) a collar secured to the outside of a pipe section spaced from one end thereof to form therewith an externally stepped tubular end,

'(b) a collar secured to the outside of a pipe section to overhang one 'end thereof to form therewith an internally stepped tubular end,

(c) means forming circumferentially spaced jaws on the radial, outer face of each of said collars arranged to interlock when said externally stepped tubular end is telescoped with said internally stepped tubular end (e) and pin means removably secured in said aperturesand projecting from the outside of said drill string into both apertures to the inside surface of the pipe section onlyto provide for unobstructed passage of said pilot bit. I a

2. In an'earth boring tool adapted for core recovery, including a hollow'main bit, a sectional tubular drill string of pipe sections having the same external size and the same internal size connected end to end .to form a smooth unobstructed inner surface'and at one end to a hollow main bit, a'pilot bit of a size to be movable into said hollow main bit through said tubular main drill string and adapted to be independently manipulated by an auxiliary drill string extending through said main drill string and connected to said pilot bit, the improvement in said earth boring tool of means for separately connecting said pipe prising,

(a) a collar secured to theoutside of a pipe section V spaced from one end thereof to form therewith an externally stepped tubular end, 7 j

(b) a collar secured to the outside of a pipe section to overhang one end thereoft-o form therewith an internally stepped tubular end, a

(c) means forming circumferentially spaced jaws on each of said tubular stepped ends arranged to interlock when said externally stepped tubular end is telescoped within said internally stepped tubular end so asto lock said pipes against relative rotation axially thereof, I V

(d) apertures formed in one of said collars and in one of said pipe ends telescoped therein located to register. when said jaws are interlocked,

(e) and pin means removably threaded into one of said apertures and projecting from the collar to be i accessible for removal or replacement from the exter ior of said drill string and into but not through the inner aperture to lock said jaws in engagement and to provide unobstructed passage for said pilot i v a 3.-In an earth boring tool adapted for core recovery, including a hollow main bit, a sectional tubular drill string of pipe sections having the'same external size and the same internal size connected end to end to form a smooth unobstructed inner surface and at one 'end to a hollow main bit, a pilot bit of a size to be movable into said hollow main bit through, said tubular main drill string and adaptedto be independently manipulated by an auxiliary drill string extendingthrough said main drill string and connected-to said pilot bit, the improvement in said earth boring tool of means for separately connecting said pipe sections end to end and to said hollow main bit comprising. a a I p (a) a collar secured to the outside of a pipe section spaced from one end thereof to form therewith an externally stepped tubular end,

(-b) a collar secured to the-outside of a pipe section to overhang one end thereof to form therewith an internally stepped tubular end, a

(c) 'means forming circumferentially spaced jaws and sockets on the radial outer face'of each of said collars arranged'to interlock withthe jaws on one I collar between jaws on the other collar when said externally stepped tubular end is telescoped within said internally stepped tubular end so as to lock said pipes against relative rotation axially thereof,

:(d)' apertures formed in one of said collars and in one of said pipe ends located to register when said jaws are interlocked, V :(e) and pin means removably'thr'eaded in One of said apertures and projecting from the collar to be accessible for removal or replacement from the exterior of said drill string and into, but not through, the inner aperture to lock said jaws in engagement and to provide 'unob'structed passage for said pilot bit; a r

References Cited by the Examiner NITED STATES PATENTS I 4,494,593 5/24 Loi 285 404 1 1,862,339' 7/32 Highmark.

2,141,880 12/38 Sat re. 2,146,100 2/39 Walch 285-404 FOREIG PATENTS 582,692 9/5 9 Canada.

BENJAMIN HERSH, Primary Examiner. BENJAMIN BENDETI, Examiner, 

1. IN AN EARTH BORING TOOL ADAPTED FOR CORE RECOVERY, INCLUDING A HOLLOW MAIN BIT, A SECTIONAL TUBULAR DRILL STRING OF PIPE SECTIONS HAVING THE SAME EXTERNAL SIZE AND THE SAME INTERNAL SIZE CONNECTED END TO END TO FORM A SMOOTH UNOBSTRUCTED INNER SURFACE AND AT ONE UNCONNECTED END TO A HOLLOW MAIN BIT, A PILOT BIT OF A SIZE TO BE MOVABLE INTO SAID HOLLOW MAIN BIT THROUGH SAID TUBULAR DRILL STRING AND ADAPTED TO BE INDEPENDENTLY MANIPULATED BY AN AUXILIARY DRILL STRING EXTENDING THROUGH SAID MAIN DRILL STRING AND CONNECTED TO SAID PILOT BIT, THE IMPROVEMENT IN SAID EARTH BORING TOOL OF MEANS FOR SEPARATELY CONNECTING SAID PIPE SECTIONS END TO END AND TO SAID HOLLOW MAIN BIT COMPRISING, (A) A COLLAR SECURED TO THE OUTSIDE OF A PIPE SECTION SPACED FROM ONE END THEREOF TO FORM THEREWITH AN EXTERNALLY STEPPED TUBULAR END, (B) A COLLAR SECURED TO THE OUTSIDE OF A PIPE SECTION TO OVERHANG ONE END THEREOF TO FORM THEREWITH AN INTERNALLY STEPPED TUBULAR END, (C) MEANS FORMING CIRCUMFERENTIALLY SPACED JAWS ON THE RADIAL OUTER FACE OF EACH OF SAID COLLARS ARRANGED TO INTERLOCK WHEN SAID EXTERNALLY STEPPED TUBULAR END IS TELESCOPED WITH SAID INTERNALLY STEPPED TUBULAR END SO AS TO LOCK SAID PIPES AGAINST RELATIVE ROTATION AXIALLY THEREOF, (D) APERTURES FORMED IN ONE OF SAID COLLARS AND IN ONE OF SAID PIPE ENDS LOCATED TO REGISTER WHEN SAID JAWS ARE INTERLOCKED, (E) AND PIN MEANS REMOVABLY SECURED IN SAID APERTURES AND PROJECTING FROM THE OUTSIDE OF SAID DRILL STRING INTO BOTH APERTURES TO THE INSIDE SURFACE OF THE PIPE SECTION ONLY TO PROVIDE FOR UNOBSTRUCTED PASSAGE OF SAID PILOT BIT. 